How would you respond to the prospect of no future generations? To the realization that human existence ends with the deaths of those now alive? Forget, for the moment, that the End Times fundamentalists wielding power these days pretty much believe that’s the case already. And how that might explain why the barren year 2027 of Children of Men — ripped by terrorism, civil war, oppression, and bad taste — seems a lot like the present day. Instead, put yourself in the position of Nigel (Danny Huston), a privileged, powerful functionary of Britain’s future tyranny. He’s poised in a living room high above a blighted Bruegelesque London skyline (is that the pig from Pink Floyd’s Animals floating by?), the Zen-like starkness of his surroundings subtly set off by the Picasso — Guernica — hanging on the wall. When asked how he feels knowing that all the priceless art treasures in his possession will be seen by no one when he’s dead, he replies, “I don’t think about it.”

Alfonso Cuarón makes you think about it. Not in a detached, philosophical way, as in P.D. James’s tart, uncompromising novel, but in pictures, sound, and action. He and four other writers are credited with the screenplay, but it’s mostly his collaboration with cinematographer Emmanuel Lubezki that has turned the book into a crackling genre movie (including the most exciting and emotionally exhausting car chase since The French Connection) made resonant and mysterious by its densely detailed, often surreal mise-en-scène.

Take Nigel. In the book he’s a major character. Here he offers an opportunity to unfold the film’s theme in a single spectacular and witty image. Otherwise, he’s a plot device, the politically powerful cousin of Theo (Clive Owen), a boozy, cynical journalist. Theo gets a surprise visit from Julian (Julianne Moore), his ex-wife from years ago, when he was a political idealist. Julian has kept the faith and is a leader of an anti-government terror organization called “The Fishes.” (In James, the Fishes are Christian and pacifist; here they are bristling with firepower.) She wants Theo to help the cause by hitting up Nigel for a travel pass to the coast for a young woman they’re eager to get to safety. Against his better judgment, and not just for the big payoff he’s offered, Theo agrees, and Nigel obliges.

So begins a harrowing chase that makes Apocalypto look like Cannonball Run II. More important, it surges into sudden, almost overwhelming moments of emotion that make it the most appropriate film to see in this Yuletide season. One such moment would have served the film well as an ending; that it continues with increasingly archetypal scenarios and imagery (a ship called Tomorrow? Please . . . ) does little to dim the overall impact. And though I’m still trying to figure out Cuarón’s point of view (at times he seems more reactionary than the staunchly Tory James), his film is pro-life in the original best sense.